Over the past decade, global efforts to prevent mother-to-child human immunodeficiency virus (HIV) transmission have been driven by rapid progress in scientific discovery, policy, and program implementation. One important advance has been the Option B+ strategy to provide lifelong antiretroviral therapy (ART) to all HIV-infected women identified during pregnancy or breastfeeding. Initially developed as a strategy for settings in which CD4 T-lymphocyte testing was not available, Option B+ is now endorsed by the World Health Organization and and its implementation has expanded to other countries worldwide.1 Although there are many clinical and operational justifications for the strategy, successful implementation of Option B+ requires substantial new investments in health infrastructure. Concerns that introduction of ambitious new services may redirect already scarce resources away from other initiatives are legitimate and warrant a careful evaluation and policy response.2